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11.
Urban Ecosystems - Urbanization poses a threat to long-lived vertebrates, particularly from road mortalities that can threaten population persistence. We studied movements, behavior and... 相似文献
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Ozone depletion potential (ODP) represents the cumulative ozone depletion induced by a particular halocarbon relative to a reference gas (usually trichlorofluoromethane, CFC-11). We focus on ODP estimation for methyl bromide. Previous attempts at its estimation have assumed that components of the ODP equation are lognormally distributed. By considering a wide range of modeling scenarios, we show that this restriction (which is based on computational convenience rather than experimental evidence) has obscured the true uncertainty in the ODP value. Moreover, when publishing point estimates for the ODP value, previous authors have given either mean or median values. We submit that a more appropriate choice for a point estimate is the mode since the distribution of ODP is skewed and since the mode is by definition, the most likely value. For each modeling scenario considered, modal values are given. In general, we find these ODP point estimates are considerably lower than those published elsewhere. 相似文献
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This article presents estimates of the sources and the extent of observation errors in different questionnaires and methods used to collect birth and death data in the 1961-63 multi-purpose sample survey of Morocco.The questionnaires used in the analysis of the three survey rounds were a list of household members (Rounds1 and 2) and a roll-call (Round3); retrospective death (Rounds1, 2, and 3) and birth (Round 3) queries; a date-of-birth tabulation (Round 2); and a household check-sheet to explain differences between Rounds 1 and 2. All available questionnaires for a given household were brought together and collated to provide several sources of information on births and deaths and a basis for assessing errors.From this analysis, the survey attempted to define the nature and to estimate the frequency of the errors which would have occurred if more restricted types of survey design had been used. Results, based on the period between Rounds 1 and 2, led to three major conclusions.First, if vital data had been collected with a single-round retrospective procedure, gross error (over enumeration plus underenumeration) would have been 17 percent for births and 36 percent for deaths. There is a net error of overenumeration of 3 percent for births (1.4 per1,000population) and 9 percent for deaths (2.3 per1,000population).Second, if two rounds were available to permit a combination of household composition follow-up and a retrospective mortality questionnaire, overenumeration would be almost entirely eliminated and underenumeration would be noticeably reduced. Third, most of the remaining errors of underestimation may be attributed to (1) an estimated number of infants born and deceased between two rounds and missed by all questionnaires, (2) matching failures caused by the absence of adults at Round 1, and (3) matching errors. 相似文献
16.
Georges A. Becus 《Revue canadienne de statistique》1977,5(1):133-139
A random generalized solution to the Robin problem for Laplace's equation is defined in terms of the sections of the random boundary data. Existence, uniqueness, and properties are established for such a solution. Particularizations to the Dirichlet and Newmann problems as well as generalization to the Robin-Poisson problem are mentioned. Applications of the results are provided. 相似文献
17.
Goulet ED Mélançon MO Dionne IJ Aubertin-Leheudre M Aubertin Leheudre M 《Journal of aging and physical activity》2005,13(3):314-326
It is unclear whether long-term aerobic (AT) or resistance (RT) training can improve insulin sensitivity (IS) beyond the residual effect of the last training bout in older women (54-78 years). Therefore, a group of nonobese, healthy older women underwent 6 months of AT (n = 8) or RT (n = 10), and the authors measured IS 4 days after the last training bouts using the hyperinsulinemic-euglycemic clamp technique. Women trained 3 days/week. AT consisted of 25- to 60-min sessions of walking/jogging at 60-95% of maximal heart rate. RT consisted of three sets of nine exercises repeated 10 times at 80% of 1 repetition maximum. AT decreased fat mass, whereas both AT and RT increased fat-free mass. Neither training program, however, improved absolute or relative rates of glucose disposal. The authors therefore concluded that nonobese, healthy older women should perform AT or RT on a daily basis in order to improve IS and maintain the improvement. 相似文献
18.
We consider a repeated electoral competition game between two parties, each representing a constituent with a given income
level. Parties are unable to commit to a policy before the election; they choose a nonlinear income tax schedule once elected.
In each period, citizens cast a vote either for the incumbent or for the challenger. We first show that there exist (pure
strategy) subgame perfect equilibria where both parties choose the most-preferred tax schedule of their constituent, subject
to the constraint that they are reelected. We characterize a specific class of these BPR (Best Policy with Reelection) equilibria
in which one of the parties plays its constituent’s unconstrained optimal tax function. Equilibrium tax schedules are always
piecewise linear. Depending on the income levels of the two parties’ constituents, we obtain either classical left-vs-right
equilibria (where the poor vote for one party and the rich for the other one) or ends-against-the-middle equilibria (where
both poor and rich vote for one party while the middle class votes for the other party). In both types of equilibria, both
parties propose the same tax schedule to a subset of the population. 相似文献
19.
We study the relationship between polygyny and HIV infection using nationally representative survey data with linked serostatus information from 20 African countries. Our results indicate that junior wives in polygynous unions are more likely to be HIV positive than spouses of monogamous men, but also that HIV prevalence is lower in populations with more polygyny. With these results in mind, we investigate four explanations for the contrasting individual- and ecological-level associations. These relate to (1) the adverse selection of HIV-positive women into polygynous unions, (2) the sexual network structure characteristic of polygyny, (3) the relatively low coital frequency in conjugal dyads of polygynous marriages (coital dilution), and (4) the restricted access to sexual partners for younger men in populations where polygynous men presumably monopolize the women in their community (monopolizing polygynists). We find evidence for some of these mechanisms, and together they support the proposition that polygynous marriage systems impede the spread of HIV. We relate these results to the debate about partnership concurrency as a primary behavioral driver for the fast propagation of HIV in some parts of sub-Saharan Africa. 相似文献
20.
Hormone-replacement therapy (HRT) attenuates the menopause-associated alterations in body composition. It is not known, however, whether this effect is a result of a concomitant increase in energy expenditure. The authors examined whether women submitted to a long-term HRT treatment presented greater energy expenditure than women who had never used HRT. We compared 13 postmenopausal women using HRT (>1 yr) with 13 age- (+/-2 yr) and body-mass-index-matched (BMI; +/-1.5 kg/m2) postmenopausal women not using HRT. Resting energy expenditure (REE; indirect calorimetry), body composition, and daily (DEE) and physical activity (PAEE) energy expenditure (accelerometry) were obtained. Although BMI, fat mass, fat-free mass, DEE, and PAEE were similar between groups, the HRT group displayed a significantly greater REE than the no-HRT group (Delta +222 kcal/day). In conclusion, the authors observed that a long-term treatment with HRT is associated with a greater REE in postmenopausal women. These results need to be confirmed. 相似文献